Katherine Russell Tsarnaev, center, wife of killed Boston Marathon bombing suspect Tamerlan Tsarnaev, exits a car at the home of her parents in North Kingstown, R.I., April 21, 2013. At left is her father, Warren Russell.

The female DNA discovered on the remains of one of the bombs that ripped through the Boston Marathon crowd earlier this month does not appear to match that of the wife of one of the bombing suspects, sources told ABC News today.

Earlier this week sources revealed that the DNA had been discovered on bomb fragments, but investigators did not know if it came from a victim in the attack, from someone who handled the bomb components before it was constructed or from a possible co-conspirator. The same day as that revelation, agents were seen leaving the home of Katherine Russell, wife of bombing suspect Tamerlan Tsarnaev, with a set of evidence bags.

Though Russell's DNA does not appear to match what was left on the bomb parts, the sources said today that the FBI still wants to know what Tamerlan may have said in a phone call to Russell days after the explosion.

An attorney for Russell released a statement Tuesday saying she was providing "as much assistance to the investigation as she can," and later said she had no prior knowledge of the plot.

Tamerlan Tsarnaev, and his younger brother Dzhokhar, stand accused of detonating a pair of bombs near the finish line of the Boston Marathon April 15, killing three people, including an 8-year-old boy, and injuring more than 260 others. Days later Tamerlan was killed in a shootout with police, but Dzhokhar was injured and later captured.

Sources told ABC News Thursday that at least for some time after his arrest, Dzhokhar was speaking with investigators and had told them the original plan for the bombing was to target a Boston Fourth of July celebration. But the young men built the explosives sooner than they expected and wanted to put them to use earlier, Dzhokhar allegedly said.

Dzhokhar also allegedly described his brother as the leader in the plan -- saying he was only brought in days before -- and reportedly told the FBI the pair constructed the bombs in the apartment Tamerlan shared with Russell.

Also this week, three 19-year-old friends of Dzhokhar's were arrested, two for allegedly trying to get rid of a laptop and a bag full of fireworks with the powder missing that belonged to Dzhokhar, and another for allegedly lying to federal investigators. The bag was found after a massive search of a landfill and an attorney for one of those young men told ABC News Thursday his client had turned over the laptop to the FBI.